OF THE MARSUPIALIA, EDENTATA, AND SIRENIA. 



185 



Oxy hemoglobin of sEpyprymnus rufescens. 



Monoclinic: Axial ratio a : b : 6 =1.4825 : 1 : 1.338; /? = 67. 



Forms observed: Prism (110), clinopinacoid (010), base (001); and, in twins, 

 positive hemiorthodome (101), orthopinacoid (100). 



Angles: Prism angle 110 A 110 = 112 (68); 001 A 010=90; 100 A 001=0 = 

 67; 100 A T01=51, from twin. 



Habit prismatic, elongated on the vertical axis, with the prism (110) and base 

 (001) alone (text figure 89) or in combination with the clinopinacoid (010) (text figure 

 90), and frequently flattened on the clinopinacoid; the base produces an oblique termi- 

 nation in all crystals. The prisms are sometimes long, but in the greater number of 

 crystals are not more than 4 to 6 times as long as wide. The orthopinacoid is not de- 

 veloped as a face and only appears in twins; hence no square crystals are seen. Twin- 

 ning is of several types, interpenetrant twins on the prism being common (text figure 

 91), see plate 22, fig. 127; twins also form on the orthopinacoid (text figure 92) (gypsum 

 type) and on the clinopinacoid similar to the carlsbad type (text figure 93). The twin 

 on the positive hemiorthodome (T01), from which the value of t was obtained, is an 

 interpenetrant twin, often seen in crystals with the combination (110) (010) (001). The 

 base of one member is nearly parallel with the orthopinacoid or prism edge of the other 

 and the acute angles are opposed with the obtuse angles pointing outward (see text 

 figure 94). In the twins of the carlsbad type the opposed prism faces on either side of 

 the plane of twinning appear to be developed more than the other pair in each case. 

 The twins on the prism are not only interpenetrant, they are frequently juxtaposed, 

 and even in this case polysynthetic (see plate 22, fig. 128). 



a/ 



a 



/90 



91 



92 



Fics. 89, 90, 91, 92, 93, 94. .Epyprymnut rufescens Oxyhcmoglobin. 



Pleochroism is very strong; a pale yellowish-red, b rather deep red, c very deep 

 red; the pleochroism is readily observed on account of the almost complete crystalliza- 

 tion of the oxyhemoglobin, leaving a nearly colorless solution. Extinction on all of the 

 usual aspects is oblique, the crystals generally presenting the clinopinacoid or prism 

 face. In the twins on the orthopinacoid, prism, and orthodome the extinction is sym- 

 metrical with the plane of twinning. The plane of the optic axes is the plane of symmetry, 

 the orientation of the elasticity axes is a A a = ll in the obtuse angle; b=&, c A 6= 12 

 in the obtuse angle. Only brushes of the interference figure in unsymmetrical arrange- 

 ment were seen on such optical sections as could be observed; the optical character 

 appeared to be negative, or Bx a a. 



KANGAROO, Macropus giganteus (?). Plate 22. 



The specimen was received from the National Zoological Park at 

 Washington during the summer and was kept frozen in the original collect- 

 ing tube until examined. The blood was rather putrid and contained many 

 small clots and amorphous matter. It had been drawn into a collecting 

 tube supplied with oxalate, hence did not clot after the specimen was 



